A constant velocity universal joint is classified into a fixed type which allows only angular displacement between two axes and a slide type which allows the angular displacement and axial direction displacement (plunging). Both types have a roller or a ball as a torque transmission component. The slide-type constant velocity universal joint for an automobile is used in a propeller shaft or a drive shaft. The drive shaft ordinarily includes the slide-type constant velocity universal joint on an inboard side and a fixed-type constant velocity universal joint on an outboard side. Because manufacturing costs are low for a “double-offset type constant velocity universal joint (DOJ-type),” which is a type of slide-type constant velocity universal joint having a ball as the torque transmission component, the DOJ-type is widely used as an inboard side joint of the drive shaft. The DOJ-type is also often used in a four-wheel drive vehicle that is capable of a high operating angle exceeding 25°.
There is a DOJ-type constant velocity universal joint that has six torque transmission balls and a DOJ-type constant velocity universal joint that has eight torque transmission balls. Between these, the DOJ-type constant velocity universal joint having six torque transmission balls is largely classified into two kinds; that of which a maximum operating angle is 25° or less and that exceeding 25°. When the maximum operating angle increases, a joint load capacity at the high angle is required to be increased as well. The joint load capacity is related to a ball groove depth and a cage thickness. Therefore, compared to the DOJ-type constant velocity universal joint of 25° or less, an outer ring outer diameter of the DOJ-type constant velocity universal joint having the maximum operating angle of 25° or more is normally about one size larger.
Conventionally, to increase the load capacity of the slide-type constant velocity universal joint, a slide-type constant velocity universal joint of which a shape of a contact ellipse between the ball groove and the ball is modified (refer to Patent Document 1), a slide-type constant velocity universal joint of which a track shape is modified by a combination of circular contact and angular contact (refer to Patent Document 2 and Patent Document 3), and a slide-type constant velocity universal joint of which offset amounts of an outer spherical surface center and an inner spherical surface center of a cage are modified (Patent Document 4) are proposed.    Patent Document 1: Japanese Utility Model Laid-Open Publication No. Showa 61-57233    Patent Document 2: Japanese Utility Model Laid-Open Publication No. Heisei 3-105725    Patent Document 3: Japanese Utility Model Laid-Open Publication No. Heisei 4-116018    Patent Document 4: Japanese Patent Laid-open Publication No. Heisei 10-73129